Upper surface flap



June 20, 1944. E. F. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 15, 1940 '7 Shets-Sheet 1 BY wk A TTORNEYJune 20, 1 944. E, F, ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 2 IN VEN TOR.

ATTORNEY June 20, 1944. ZAP

UPPER SURFACE FLAP Filed Jan. 13 I 1940 '7 Sheets-Sheet 3 o 6 T m w 1m Em F. 5

BY fl ATTORNEY June 20, E F ZAP UPPER SURFACE FLAP Filed Jan. 15, 1940 7Sheets-Sheet 4 EE ZAP,

IN VEN TOR.

Mar

ATTORNEY June 20, 1944. E. F. ZAP

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 5 E1 ZAP)INVENTOR. BY

ATTORNEY June 20, 1944. E. F. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 7 Sheets-Sheet 6 o .n- 1 kIII-III VII-III III...

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III, n- I" m I ATTORNEY June 20, 1944. ZAP 2,352,062

UPPER SURFACE FLAP Filed Jan. 13, 1940 '7 Sheets-Sheet '7 wullllll VINVENTOR. I Z: 7728 I A TTORNEY Patented June 20, 1944 UNITED STATESPATENT OFFICE UPPER SURFACE FLAP Edward F. Zap, Los Angeles, Calif.

Application January 13, 1940, Serial No. 313,770

7 Claims.

This invention relates to an airfoil the lift or lift capacity of whichas well as its drag can be changed, either throughout the entire airfoilor through the center portion or tip portions thereof.

It is the object of the invention to provide such changeable airfoilhaving the following advantages: The production of a small lift isassociated with a. small drag; the production of a large lift isassociated with the production of either a large drag or a comparativelysmall drag, as desired at any time by the pilot. The airfoil requiressmall control forces only. The control effects or aerodynamic changesare large. When used for lateral control, the lateral control momentproduced by the airfoil is associated with a favorable yawing moment orat least hardly any adverse yawing moment. The improved airfoil isrelatively free of icing danger. Th control effect has no appreciabletime lag. The airfoil is structurally simple, sturdy, and light, it ismechanically reliable, it affords good access for the inspection of themoving parts, and the latter are well protected against accidentaldamage.

These objects are accomplished by bifurcating the trailing end of theairfoil, that means giving it two trailing edges one above the other, anupper airfoil lip and a lower airfoil lip, which may be integral withthe airfoil or movable relative thereto. A thin movable fiap'is placedinto the pocket formed by and between the two lips. This flap extendsforwardly and upwardly into the pocket, being spaced from the lower lip,particularly for the high lift condition, affording thereby a good sizeentrance to the pocket. The fiap is normally in contact with the upperlip, and for the high lift condition is brought into spaced relationthereto, be it by the displacement of the flap, by the displacement ofthe lip, or both. An air passage between the flap and the airfoil isthus formed. The flap cooperates aerodynamically with the upper airfoilsurface, its airflow-exposed portion being in continuation thereof.

The simpler embodiments of my invention, with fixed lips and simple fiapmotion, confer appreciable benefits on the air-place, and elucidate thebroad principles involved. It is contemplated to employ movable lipstogether with composite fiap motion, in order to obtain the highestefiiciency. It will also be explained and illustrated how the inventionmay be combined with a. two way exit slot as described per se in mypending applications Ser. Nos. 195,381 and 292,726.

This will now be illustrated and described in the accompanying drawingsand the following specification.

Since the underlying principles '5 may be incorporated in still otherspecific devices, it is not intended to be limited to the ones hereshown, except as such limitations are clearly imposed by the appendedclaims.

In the drawings, like numerals refer to similar parts throughout theseveral embodiments and views, of which Figs. 1 and 2 represent crosssectional views taken vertically and in the direction of flight, of anairfoil incorporating the invention, Fig. 1 represents the flapretracted and Fig. 2 represents the flap extended into its high liftposition.

Figs. 3 and 4 are like views of a second embodiment, in which the upperlip is elastic.

Figs. 5 and 6 are like views of a third embodiment, in which the flap isshaped different from that in Figs. 1 and 2.

Fig. 7 is a like view of a fourth embodiment with the flap being mountedin a different manner,

the full lines indicating the low lift position of the flap, and thedashed lines its high lift position.

Figs. 8 and 9 are like views of a fifth embodiment, the fiap beingdifferently constructed.

Fig. 10 represents a plan view of the airfoil as seen from top, showingthe application of the invention for lateral or aileron control.

Figs. 11 to 13 represent in cross sectional View taken vertically and indirection of flight a sixth embodiment of the invention, in which forthe low lift condition a trailing edge van-e closes the gap between theflap and the lower lip. Fig. 11 corresponds to the landing condition,Fig. 12 to the take-off condition, and Fig. 13 to the low lift and highspeed condition.

Figs. 14 to 16 represent in like view a seventh embodiment, in which aforwardly or rearwardly opening slot is provided in association with theupper lip. The flap vane is movable independent-1 1y of the flap motion.Fig. 14 shows the flap retracted, Fig. 15 is equivalent to aileron up,"and Fig. 16 to aileron down."

Figs. 17 to 20 represent in like view an eighth embodiment in which theflap is mounted for composite motion and the two lips are movable. Figs.17 and 18 show the flap retracted, with the upper lip in differentposition. Fig. 19 shows the flap extended, and Fig. 20 shows the flapextended and deflected.

Figs. 21 and 22 represent in like view a ninth embodiment in which theflap is mounted for single motion, and the two lips are independentlymovable. Fig. 21 shows the flap retracted, and Fig. 22 shows the flapextended.

Referring now to these drawings and particularly to Figs. 1 and 2,numeral ll denotes broadly a major fixed airfoil, to which is hinged a.flap 20 at the hinge 2|. The airfoil contour or profile shows a convexleading edge l4, a convex evenly rounded upper camber line I2 and asimilar,

convex, evenly rounded lower camber line l3.

upper and of the lower airfoil walls or coverings respectively suitablybraced and stiffened as by ribs 28, or elastically or movably mounted orfastened, as will be illustrated with reference to the differentembodiments. In the first embodiment, Figs.1 and 2, both lips are rigidand fixedly mounted.

The upper lip and the lower lip form and enclose a rearwardly openspanwise extending pocket 22. Front portion 24 of flap 20 is positionedwithin pocket 22, its rear portion ex-' tending out into the open spacebehind the pocket. For the low lift condition, the rear, airflow-exposedflap portion 23 is in line and flush with the upper camber line [2. Atthe trailing edge 25 of the upper lip IS, the fiap 20 makes tightcontact with the air-foil. Front flap portion 24 is positioned withinthe pocket between the upper and lower lip. The flap is held andstiffened by flap ribs 33 which extend to a hinge point 2| about whichthe flap is rotatable. By means ofthat hinge, the fiap is mounted on thelower lip l'l. Reciprocating control push-pull rod 30 hinged to the flapat 3| is subject to the pilots manipulation in any conventional mannernot shown, and constitutes control means for turning the flap intodifferent positions relative to the airfoil ll. Thus, a rearward motionof push-pull rod 30 turns flap 20 rearwardly as well as down, from thelow lift position Fig. 1, where the trailing flap edge 26 is in linewith the upper and lower camber lines l2 and I3, 26 being on thegeometric line 29 forming a geometric projection or extension of lowercamber line l3, into the high lift position Fig. 2, trailing edge 26then being positioned below the extension line 29 of the lower camberline. It will also be noted that rear flap portion 23 is then downwardlyand rearwardly inclined relative to the upper camber line l2, as shownin Fig. 2, whereas in Fig. 1 it is in line therewith.

The arrangement of Figs. 3 and 4 differs from that in Figs. 1 and 2 bythat the rigid upper lip I9 is replaced by an elastic upper lip I8, madeof thin metal or other sheet, and fastened to the rear spar I6. Theforward flap portion 24 is provided with projections or teeth 21 nearits leading edge, which in the low lift position Fig. 3 are spaced fromlip l8 and positioned within pocket 22. If the rear portion of the flapis turned down, its front portion together with teeth 21 is lifted up,and said teeth make contact with the upper lip l8, whereby the teethdeflect the upper lip upwardly from its low lift position. Thereby. anarrow rearwardly opening slot 40 is formed between the upper lip andthe rear flap portion, which slot connects the space above the airfoilwith the pocket 22. Air will then enter into the pocket from below,through the gap between the trailing edge of the lower lip I! and theflap, and will leave the pocket in rearward fiow through the slot 40. Ihave found that this has a distinctly beneficial effect on theaerodynamic force created.

In the airfoil variation shown in Figs-5 and 6, the same opening andclosing of the slot is obtained with a stiff or rigid upper elastic lip,the lip being in that respect like the one shown in Figs. 1 and 2. Thefront flap portion 24 joins the rear flap portion 23 with a sufficientlycurved bent slot to effect the opening of slot 40 by virtue of its shapeas the fiap is moved backwardly from lip edge 25, and to effect aclosing of slot 40 as the flap 20 is moved forwardly towards and intocontact with the upper lip 19.

In the arrangement of Fig. 7, the opening and closing of the slot iseffected in exactly the same manner as in the variation just described.This arrangement differs from the one of Fig. 5 merely by the positionof the axis of rotation of the flap. This axis is now positioned belowthe airfoil, at a point designated by 2|. The flap is held by rollers 5|and 52 guided in a bent slot 53 spared out of a rigid wing rib. Ofcourse, any other supporting and moving arrangement adapted to make theflap movable in the manner described would equally well serve for takingthe invention into use.

Thus, in Figs. 8 and 9, a stationary, spanwise extending, fixed flapsupport is shown. This support 50 is fastened to the airfoil structure,and serves as a stationary flap portion. Flap 20 is held by rollers 5iand adapted to slide on top of and along flap support 60. Support 60 isseparated from the upper lip l9 by the slot 40. In the low liftposition, flap 20 is moved rearwardly as shown in Fig. 9, and slot 40 isopen. Air enters then from below through the gap between fiap 20 and/orsupport 50 and lower lip I1 into pocket 22 and is discharged rearwardlythrough slot 40.

The following figures illustrate more elaborate embodiments of myinvention for utmost aerodynamic efficiency at the cost of somestructural complications. In the embodiment of the invention, Figs. 11to 13, upper lip 50 is not rigidly fastened to the airfoil but it ishinged thereto about a spanwise axis or hinge 49. The rotatable upperlip 5i!v is provided with a horn 54 to which is hinged the push-pull rod55, which in turn is under the control of the pilot in any conventionalmanner not shown in the drawings. This brings about that theslot 40 isseparately under the control of the pilot which makes the airplane moremaneuverable. If upperJip 50 is displaced from its neutral positionrepresented by the solid line in Fig. 12 through a large angle ofdisplacement say into the position represented by the dotted line ofFig. 12, the lip vane 50 acts as a spoiler, diminishing the lift rapidlyand thoroughly; this provides a welcome means for assisting the landing.If the same lip vane is displaced through a small angle of displacement,in combination with the high lift position of the flap, as shown in Fig.11, the lift is increased in that so-called stalling or burbling of theairflow is delayed to a larger angle of attack. In the arrangement Figs.11 to 13, a separate control for the lip vane and for the flap, in alltwo separate controls for the mechanisms shown, are contemplated.

In the same Figs. 11 to 13 there is furthermore illustrated use of aflap vane 4|, hinged to the flap along the trailing edge 26. A guide rod43 rigidly fastened to flap vane 4|, extending therefrom forwardly, isprovided for securing the de-- sired angular position of the flap vane.This rod 43 has at its forward end a guide pin 44, which 'in its turn isin operative sliding engagement with guide slot 42, spared out of anairfoil rib. Slot 42 is shaped to turn vane 4| into close contact withflap 2!! flush thereto for the high lift position illustrated in Fig.11; flap and vane forming then in effect together one unitary sheet. Atthe low lift position Fig. 13, vane 4| declines relative to the flap,contacting the lower lip flush therewith, and closing the gap betweenthe flap and the lower lip. This improves the streamlining for the lowlift (high speed) condition and diminishes the drag or air resistance.In the arrangement Figs. 11 to 13, no separate control for the flap vaneis contemplated, but the flap and vane move together in linked relation,so that every flap position is associated with a predetermined flap vaneposition.

In Figs. 14 to 16, showing the low lift position of the flap only, aneven higher degree of refinement is illustrated. The upper lip vane isconstructed to either close the upper gap, or to open a rearwardly openslot (Fig. 16), or to open a forwardly open slot (Fig. 15). This isachieved by employing a doubly opening vane 35 having an inwardlyextending born 38 and a pushrod 39 hinged to the horn. The detail of themechanism including means for mounting and fastening the vane 36 is notshown, as the same is already disclosed in my copending application Ser.No. 195,381 and Ser. No. 292,726.

Flap vane 4| is'likewise separately controlled. The guide slot 45 is nowspared out of a separate guide piece 56 hinged at its rear end 51 to theairfoil structure. Guide piece 56 can be turned by means of bell crank46 mounted on the airfoil structure at 41; the one bell crank armengaging the guide piece and the other bell crank arm being hinged topush rod 48, said rod being under the control of the pilot in anyconventional manner not shown in the drawings. As the guide piece 56 isdeflected, flap Vane M is likewise turned, even while flap 20 may remainstationary. It must be clearly understood that the embodiment Figs. 14to 16 requires three different and separate controls for the movablesurfaces shown, one for moving flap 20, through pushrod 30, one formoving flap vane 4|, through pushrod 48 and a third for moving the uppervane 36 through pushrod 39. It is however feasible to reduce the numberof controls needed by interlinkage. Pushrods 48 and 39 can for instancebe linked together, and employed together for aileron or lateralcontrol. The flaps are then arranged as schematically shown in Fig. 10,and the control action on the right wing and on the left wing iscounterwise as with ordinary ailerons.

Fig. 1'7 to 22 illustrate a flap with composite motion, both lips beingtiltable, and the lower lip being linked to the flap motion mechanism.Flap 20 is provided with a plurality of roller guide channels 65 inengagement with and held by rollers 63 and 64. These rollers are mountedon flap support Bl, which support in turn is hinged to the stationaryairfoil structure at 62. Flap support horn 66 connects to the controlgear by a push-pull rod hinged thereto and not shown in the drawings.Lower lip I1 is hinged at 61 to the lower airfoil surface. It is linkedto the flap support 6| by means of link members 68 hinged at one end tothe flap support and at the other end to the lower lip ii.

The flap can thus be moved into three principal positions, (a) flapretracted, Figs. 17 and 18, (-b) flap extended but not deflected, Fig.19, the

flap support being still in its neutral position as in Fig. l! andaccordingly the lower lip too, and (c) the flap extended and deflected,the flap support being turned down and the lower lip likewise by virtueof the linkage through member 68.

Figs. 21 and 22 illustrate a flap mounted slidably on a stationary flapsupport for single motion. Both lips can be tilted independently of eachother and of the flap motion. The rollers 63 and 64 are now mounted onthe stationary flap support 69 and are in engagement with the rollerchannels 65 fastened to the flap 20. Lower lip l1 consists of a vanehinged to the stationary airfoil structure at 10, and a push-pull rod(not shown) is hinged to the lower lip horn l l.

The last described two arrangements are very suitable for use as highlift device in combination with aileron use by means of counterwisecontrol at the wing tips as schematically illustrated in Fig. 10. Thedifferent positions of the upper lip and of the flap in combination withthe lower lip are as follows:

I. Normal flight: Flap retracted.

Ia. Aileron neutral: Upper lip closed, as in Fig. 17, upper lip indotted line.

Ib. Aileron up; Upper lip all way tilted, as Fig. 17, upper lip in solidline.

10. Aileron "down: Upper as Fig. 18.

II. Take off and climb: Flap extended but not deflected.

IIa. Aileron neutral: Upper lip closed.

IIb. Aileron up: Upper lip all way up, as Fig. 19, upper lip in solidline.

He. Aileron down: Upper lip partially opened, as Fig. 19 upper lip indotted line.

III. Landing condition: Flap extended and deflected.

IIIa. Aileron open, as Fig. 20.

I111). Aileron up": Upper lip all way up.

IIIc. Aileron down: Upper lip partially open, as Fig. 20.

lip partially tilted,

neutral: Upper lip partially I have obtained best results by making thev flap chord from 20% to 25% of the airfoil chord. In the high liftposition, the upper lip should overhand the flap by not less than 2% ofthe chord, and the slot 40 should not be narrower than 2% of the chord.

I claim:

1. In an aircraft, an airfoil with continuously curved upper and lowersurfaces terminating in a trailing substantially spanwise extendingrearwardly projecting upper airfoil lip and in a trail,- ingsubstantially spanwise extending rearwardly projecting lower airfoillip, a substantially spanwise disposed than the distance between theupper airfoil lip and the lower airfoil lip, movably mounted behind theairfoil and in all positions partly within the pocket formed by andbetween said upper airfoil lip and said lower airfoil lip so that theleading edge of the flap is forward of the two flap much thinnerthroughout I foil lip and in contact curved upper and lower surfacesterminating in a trailing substantially spanwise extending rearwardlyprojecting upper airfoil lip and in a trailing substantially spanwiseextending rearwardly projecting lower airfoil lip, a substantiallyspanwise disposed flap much thinner throughout than the distance betweenthe upper airfoil lip and the lower airfoillip,rotatablymounted behindthe airfoil and in all positions partly within the pocket formed by andbetween said upper airfoil lip and said lower airfoil lip so that theleading edge of the flap is forward of the two trailing edges of the twolips, the flap being in all positions in spaced relation to the lowerairfoil lip and in contact with the upper airfoil lip, theairflowexposed rear portion of the upper flap surface and the upperairfoil surface joining substantially flush with each other so as toform together a substantially continuously curved upper surface, andmeans for rotating said flap.

3. In an aircraft, an airfoil with continuously curved upper and lowersurfaces terminating in a trailing substantially spanwise extendingrearwardly projecting upper airfoil lip and in a trailing substantiallyspanwise extending rearwardly projecting -lower airfoil lip, and asubstantially spanwise disposed flap much thinner throughout than thedistance between the upper airfoil lip and the lower airfoil lip,movably mounted behind the airfoil and in all positions partly withinthe pocket formed by and between said upper airfoil lip and said lowerairfoil lip so that the leading edge of the flap is forward of the twotrailing edges of the two lips, the flap being in all positions inspaced relation to the lower airfoil lip and in contact with the upperairfoil lip, the airflow-exposed rear portion of the upper flap surfaceand the upper airfoil surface joining substantially flush with eachother so as to form together a substantially continuously curved uppersurface.

4. In an aircraft, an airfoil with continuously curved upper and lowersurfaces terminating in a trailing substantially spanwise extendingrearwardly projecting upper airfoil lip and in a trailing substantiallyspanwise extending rearwardly projecting lower airfoil lip, and asubstantially spanwise disposed flap much thinner throughout than thedistance between the upper airfoil lip and the lower airfoil lip,movably mounted behind the airfoil and in all positions partly withinthe pocket formed by and between said upper airfoil lip and said lowerairfoil lip so that the leading edge of the flap is forward of the twotrailing edges of the two lips, the flap being in all positions inspaced relation to the lower airwith the upper airfoil lip, theairflow-exposed rear portion of the upper flap surface and the upperairfoil surface joining substantially flush with each other so as toform together a substantially continuously curved upper surface.

5. In an aircraft, an airfoil with continuously curved upper and lowersurfaces terminating in a trailing substantially spanwise extendingrearwardly projecting upper airfoil lip and in a trailing substantiallyspanwise extending rearwardly projecting lower airfoil lip, asubstantially spanwise disposed flap much thinner throughout than thedistance between the and the lower airfoil forward of the two trailingedges of the two lips, the flap being in all positions in spacedrelation to the lower airfoil lip and in contact with the upper airfoillip, the airflow-exposed rear portion of the upper flap surface and theupper airfoil and positioned behind all positions partly within thepocket formed by and between said upper airfoil lip and said lowerairfoil lip so that the leading edge of the flap is forward of the twotrailing edges of the two lips, the flap being in all positions inspaced relation to the lower'airfoil lip and in contact with the upperairfoil lip, the airflow-exposed rear portion of the upper flap surfaceand the upper airfoil surface joining substantially flush with eachother so as to form together a substantially continuously curved uppersurface.

EDWARD F. ZAP.

